Hydrocarbons, such as fossil fuels (e.g. oil) and natural gas, are extracted from underground wellbores extending deeply below the surface using complex machinery and explosive devices. Once the wellbore is established by placement of cases after drilling, a perforating gun assembly, or train or string of multiple perforating gun assemblies, are lowered into the wellbore, and positioned adjacent one or more hydrocarbon reservoirs in underground formations. The perforating gun has explosive charges, typically shaped, hollow or projectile charges, which are ignited to create holes in the casing and to blast through the formation so that the hydrocarbons can flow through the casing. Once the perforating gun(s) is properly positioned, a surface signal actuates an ignition of a fuse, which in turn initiates a detonating cord, which detonates the shaped charges to penetrate/perforate the casing and thereby allow formation fluids to flow through the perforations thus formed and into a production string. The surface signal typically travels from the surface along electrical wires that run from the surface to one or more detonators positioned within the perforating gun assembly.
Assembly of a perforating gun requires assembly of multiple parts, which typically include at least the following components: a housing or outer gun barrel within which is positioned an electrical wire for communicating from the surface to initiate ignition, a percussion initiator and/or a detonator, a detonating cord, one or more charges which are held in an inner tube, strip or carrying device and, where necessary, one or more boosters. Assembly typically includes threaded insertion of one component into another by screwing or twisting the components into place, optionally by use of a tandem adapter. Since the electrical wire must extend through much of the perforating gun assembly, it is easily twisted and crimped during assembly. In addition, when a wired detonator is used it must be manually connected to the electrical wire, which has lead to multiple problems. Due to the rotating assembly of parts, the wires can become torn, twisted and/or crimped/nicked, the wires may be inadvertently disconnected, or even mis-connected in error during assembly, not to mention the safety issues associated with physically and manually wiring live explosives.
According to the prior art and as shown in FIG. 1, the wired detonator 60 has typically been configured such that wires must be physically, manually connected upon configuration of the perforating gun assembly. As shown herein, the wired detonator 60 typically has three (or more) wires, (although it is possible to have one or more wires whereby one wire could also be a contact (as described in greater detail below and as found, for instance, in a spring-contact detonator, commercially available from DynaEnergetics GmbH & Co. KG without the benefit of selectivity) and whereby a second connection would be through a shell or head of the detonator), which require manual, physical connection once the wired detonator is placed into the perforating gun assembly. For detonators with a wired integrated switch for selective perforating, the wires typically include at least a signal-in wire 61, a signal-out wire 62 and a ground wire 63, while it is possible that only two wires are provided and the third or ground connection is made by connecting the third wire to the shell or head of the. In a typical manual, physical connection, the wires extending along the perforating gun are matched to the wires of the detonator, and an inner metallic portion of one wire is twisted together with an inner metallic portion of the matched wire using an electrical connector cap or wire nut or a scotch-lock type connector.
The detonator assembly described herein does away with the wired connection by providing a wirelessly-connectable, selective detonator, more specifically, a detonator configured to be received within a detonator positioning assembly through a wireless connection—that is, without the need to attach wires to the detonator. For the sake of clarity, the term “wireless” does not refer to a WiFi connection. The detonator assembly described herein solves the problems associated with the wired detonator of the prior art in that it is simple to assemble and is almost impossible to falsely connect.